Such an installation with at least one filter unit is generally known and normally comprises a set of carbon filters with active carbon which is able to remove from the waste gases possible contaminants therein. National and international environmental standards increasingly require the use of such filters to ensure that possible harmful waste gas components do not enter the environment. Active carbon filters provide only a partial solution herefor. The operation thereof is based on adsorption of harmful components to the carbon surface. This must therefore preferably be as large as possible, which means in practice that the waste gases are carried through a porous bed of active carbon. Although a large part of the harmful constituents can thus be removed per se from the waste gases, this produces a significant resistance in the outflow of the waste gases. The carbon bed therefore has to be relatively voluminous so that this resistance does not rise to unacceptable levels, which is expensive. The filter moreover becomes saturated relatively quickly, whereby the effectiveness of the filter will eventually decrease significantly. In order to avoid the filtering action finally becoming inadequate, the filter has to be changed before this occurs, for which purpose the installation usually has to be taken out of operation.
The above stated drawbacks do not affect a filter installation of the type stated in the preamble as known from the Netherlands patent application no. 1000918. The filter installation described therein is based on a filter unit having therein a liquid bath of an active filtering liquid. The period of operation of such a liquid bath can be considerably longer than that of a carbon filter, while after a period of time the quantity of liquid can be replenished in simple manner from outside or otherwise without the installation having to be taken out of operation. The operation of this installation is based on a chemical interaction between the waste gases and the odour-neutralizing liquid, whereby harmful components in the waste gases are intercepted and converted in the airflow. A superficial contact between the waste gases and the liquid is already found to be sufficient for this purpose, so that the resistance of such an installation in the flow path of the waste gases can remain limited. A significant part of the undesired components in the waste gases can thus be removed therefrom. A drawback of such a liquid filter is however that the operation thereof is to a greater or lesser degree specific to determined components or groups of components in the waste gases, depending on the specific choice of the filtering liquid, whereby sometimes in practice not all undesired components can be removed effectively from the waste gases.